1. Field of the Invention
The present invention relates to a signal generating device that generates a signal notifying a device user of a state change of the device, an event occurrence and the like and a mechanical apparatus having the signal generating device.
2. Description of the Related Art
Excessive speed warning for a car, wrong operation warning used in machinery for industrial use, overrun warning for control values, such as pressure or temperature, used in a manufacturing premise and the like must invite user's attention without fail even under a noisy environment. In addition to the above warnings, for example, in the case of a mobile phone, it is preferable that information for notifying a user of a state change of a device or new arrival of information such as incoming call or mail reception easily invite user's attention even under a noisy environment, for example, in and out of a mobile object such as a motor bus, a train, a car, or in a public space.
It is assumed that wrong operation warning or mail arrival notification in a personal computer is delivered to the user in a form of “sound”. In this case, the warning or notification sound cannot be turned up in order to maintain silence in an office or the like. On the other hand, if a use environment is noisy, the warning or notification sound is output at a large volume comparing favorably with surrounding noise, operational noise of machine to try to invite the user's attention. However, a large volume of warning or notification sound becomes new “noise” for other users (operators or workers).
Further, in the case of a mobile electronic device, warning or notification sound is generated even when the device user is in motion, in a walking state, or the like as long as the device is running. Therefore, the warning or notification sound must be easily perceived by the user even when the user is in an environment subject to noise or vibration.
That is, generation of the warning or notification sound that can easily invite the user's attention even under whatever circumstances is demanded. For example, Jpn. Pat. Appln. Laid-Open Publication No. 11-249673 discloses a technique of applying amplitude modulation using envelops curve function having a pulse-like rhythm to a carrier within an audible range so as to output it and combining two or more of the following elements: the vibration number of the carrier; the amplitude of the carrier; the pulse speed of envelops curve function used in amplitude modulation; and the pulse width of envelops curve function used in amplitude modulation, to synchronously change the carrier, thereby generating an warning that can be easily distinguished even under a noisy environment.
The above technique of Jpn. Pat. Appln. Laid-Open Publication No. 11-249673 intends to make the user easily distinguish the warning sound by synchronously changing the rise and fall or volume of the warning sound. Even in this case, however, the warning sound may not reliably be perceived by the user if he or she concentrates on a task or the like, as in the case with an ordinary warning sound. Further, since being easily distinguished not only the user whose attention needs to be attracted but also other users surrounding the target user, the warning sound according to this technique is not adequate in the situation where the warning or notification needs to be directed only to a specified user under an environment in which a plurality of users use a plurality of apparatuses, leading to confusion of the warning or notification sound emitted from the plurality of apparatuses.